Getting To The Heart Of A Baofeng

November 15, 2022 by Dan Maloney 32 Comments

In amateur radio circles, almost no single piece of equipment serves as more of a magnet for controversy than the humble Baofeng handheld transceiver. It’s understandable — the radio is a shining example of value engineering, with just enough parts to its job while staying just on the edge of FCC rules. And at about $25 a pop, the radios are cheap enough that experimentation is practically a requirement of ownership.

But stripped down as the Baofeng may be, it holds secrets inside that are even more tempting to play with than the radio itself. And who better than [HB9BLA], a guy who has a suspiciously familiar Swiss accent, to guide us through the RF module at the heart of the Baofeng, the SA818. For about $8 you can get one of these little marvels off AliExpress and have nearly all the important parts of a VHF or UHF radio — an SDR transceiver, a power amp, and all the glue logic to make it work.

In the video below, [Andreas] puts the SA818 module through its paces with the help of a board that pairs the module with a few accessories, like an audio amp and a low-pass RF filter. With a Raspberry Pi and a Python library to control the module, it’s a decent imitation of the functionality of a Baofeng. But that’s only the beginning. By adding a USB sound card to the Pi, the setup was able to get into every ham’s favorite packet radio system, APRS. There are a ton of other applications for the SA818 modules, some of which [Andreas] mentions at the end of the video. Pocket-sized repeaters, a ridiculously small EchoLink hotspot, and even an AllStar node in an Altoids tin.

Of course, if you want to get in on the fun, you’re going to need an amateur radio license. Don’t worry, it’s easy — we’ll help you get there.

Continue reading “Getting To The Heart Of A Baofeng” →

Power Up Vintage Electronics Less Unsafely With A Dim-Bulb Tester

November 13, 2022 by Donald Papp 54 Comments

Plugging in something like an antique radio to see if it works is a good way to have a bad time, because some old components don’t age well. For vintage electronics, inspection and repair are steps one and two. When it comes time to cautiously apply power, it’s best to use what’s called a dim-bulb tester and most hackers can probably put one together from scrap.

Being able to use one (or both) bulbs adds some flexibility, and the embedded power monitor is an inexpensive and handy addition.

These testers make it easier, and safer, to tell if there are any big problems with a device’s power supply. In its simplest form, a dim-bulb tester puts an incandescent lamp in series between a device — like an old radio — and the AC power from a wall socket. Thanks to this, if the device has a short circuit, the bulb will simply light up instead of causing any damage.

Ideally, one uses a bulb with a wattage rating that is roughly equal to the power consumption of the device being tested. If all is well, the bulb will glow very faintly and the device will work normally. A brightly glowing bulb would indicate excessive current draw. To allow some flexibility, [Doz]’s tester design allows using one or two 60 W incandescent bulbs in series, and even incorporates an inexpensive power monitor.

A dim-bulb tester isn’t an in-depth diagnostic tool but it is effective, simple, and allows for a safe startup even if there’s a serious problem like a short. It helps protect valuable hardware from going up in smoke. In fact, the fundamental concept of limiting power to protect hardware in case of a fault has also been applied in the world of retrocomputing, where it helps protect otherwise irreplaceable hardware if something goes wrong.

PCB antenna rendered useless by overly enthusiastic copper fill.

The Many Ways You Can Easily Ruin Your PCB Antenna Design

November 1, 2022 by Maya Posch 28 Comments

PCB antenna impaired by copper fill and other attenuation sources.

We have all seen Printed Circuit Board (PCB) antennas: those squiggly bits of traces on PCBs connected often to a Bluetooth, WiFi or other wireless communication chip. On modules like for the ESP8266 and ESP32 platforms the PCB antennas are often integrated onto the module’s PCB, yet even with such a ready-made module it’s possible to completely destroy the effectiveness of this antenna. These and other design issues are discussed in this article by [MisterHW].

It covers a range of examples of poor design, from having ground fill underneath an antenna, to having metal near the antenna, to putting dielectric materials near or on top of the antenna. The effect of all of these issues is generally to attenuate the signal, sometimes to the point where the antenna is essentially useless.

Ultimately, the best PCB antenna design is one where there is no nearby copper fill, and there are no traces running near or on layers below the antenna. After all, any metal trace or component is an antenna, and any dielectric materials will dampen the signal. Fortunately, there is e.g. a free KiCad library with ready-to-use PCB antenna designs to help one get started with a custom design, as well as many other resources, covered in the article.

If you want to get really professional about checking the effectiveness of an antenna design, you’ll want to use a Network Vector Analyzer. These will also help you with tuning the capacitors used with the PCB antenna.

(Featured image: PCB antenna rendered useless by overly enthusiastic copper fill.)

Identify That Antenna By Sight

November 1, 2022 by Jenny List 75 Comments

It’s a skill that radio amateurs pick up over years but which it sometimes comes as a surprise to find that is not shared by everyone, the ability to casually glance at an antenna on a mast or a rooftop and guess what it might be used for. By which of course I mean not some intuitive ability to mentally decode radio signals from thin air, but most of us can look at a given antenna and immediately glean a lot of information about its frequency and performance. Is this privileged knowledge handed down from the Elmers at the secret ceremony of conferring a radio amateur’s licence upon a baby ham? Not at all, in fact stick around, and I’ll share some of the tricks. Continue reading “Identify That Antenna By Sight” →

Direction-Finding With Help From The Steam Deck

October 21, 2022 by Bryan Cockfield 6 Comments

Direction-finding, or fox hunting, is a popular activity in ham radio circles where a group of people armed with radios attempt to locate a broadcasting source. Besides being a hobby for amateurs, it’s also a necessary tool in the belt of regulators who are attempting to track down violators of the air space. There are a lot of ways to figure out the precise location of a radio transmission, but this one manages to pull it off using both a boat and a Steam Deck, each armed with a software-defined radio.

This project comes to us from [Aaron] who is well known in the amateur radio circles for his SDR-focused Linux distribution called DragonOS; which has all the tools needed for a quality SDR experience, in this case KrakenSDR and DF Aggregator. He’s loaded everything up on a Steam Deck and left that in a secure location on the shore of a lake, while he carries second device with the same software with him on a boat. With the two devices listening for a specific signal, he’s able to quickly zero in on his friend on the shore who is broadcasting on the 70 cm band thanks to the help of all of these software packages.

While ham radio isn’t always known for being a youthful and exciting activity, the advent of software-defined radio and other digital modes seem to be shaking things up in that world. Certainly speeding around a lake on a boat is fun on its own as well, and a fox hunt like this can be done with something as small and simple as a Raspberry Pi too.

Continue reading “Direction-Finding With Help From The Steam Deck” →

Permeability Tuned Oscillators Made Stable With A Glue Stick

October 19, 2022 by Jenny List 17 Comments

For over a century now, radio amateurs have made tuned circuits using a coil of wire and a variable capacitor. In recent decades the supply of variable capacitors has dwindled, as SDR technology has supplanted the traditional tuning capacitor. No more tuned circuits for the radio amateurs? Not quite, as [Bill Meara N2CQR] shows us in the video below the break by making variable inductors using permeability tuning. This is hardly high-tech, the major component is as simple as a glue stick.

A permeability tuned inductor has a core that is moved in and out of its center by means of a screw. A glue stick has a glue core on a lead screw from a knob at its end, so an old glue stick with the glue replaced by a ferrite ring makes a reasonable permeability tuned former. The coil is wound on its outside, and when assembled into an oscillator it gives a useful tuning range. This is hardly a new idea as permeability tuning could be found in car radios and TV tuners among other applications back in the day, but it’s still a good trick to bear in mind.

We’ve featured plenty of Bill’s videos before here at Hackaday, most recently tracking down an unusual early TV.

Continue reading “Permeability Tuned Oscillators Made Stable With A Glue Stick” →

Generating Stereo FM Signals, Thanks To Python

October 19, 2022 by Dan Maloney 7 Comments

A casual understanding of how AM radio works is pretty easy to come by, and standard FM is only a little more complicated. Things can go off the tracks a bit with stereo FM, though — figuring out how they squeeze two separate audio tracks onto one radio signal is a bit of a head-scratcher. In that case, wrapping your head around the concept might be helped by mocking up a stereo FM signal with an arbitrary waveform generator and a little bit of Python.

Not that [Sebastian] of Baltic Lab was unfamiliar with multiplex FM theory, mind you. As he explains it, his goal was to generate a valid stereo FM signal with a different pure tone on each channel, 700 Hz on the left and 2,200 Hz on the right. Luckily, [Sebastian] has a nice AWG, the Siglent SDG1032X, which has an Ethernet connection that can be used to control it remotely along with PyVISA, a Python package for controlling instruments using the Virtual Instrument Software Architecture protocol.

The meat of this project, and what really helps drive home the concept of putting multiple audio signals onto an FM signal, lies in the Python code that generates the component parts. [Sebastian] does a great job explaining how he programatically generates the sum and difference signals along with the 19 kHz pilot tone, and puts them all together into one waveform. The output of the program is used to generate a series of values that are sent to the arbitrary waveform generator, which outputs the desired FM signal. Looking at the output on a spectrum analyzer, the two audio tones are clearly visible, as are the attenuated pilot tone and some other spikes a little further up.

Just add an antenna to the setup and you’d have the world’s dullest FM radio station — but at least it’d be in stereo. Or if you want to check out the origin story for FM radio, we’ve got something for that too.